1. Field of the Invention
The present invention relates to boot soles and more particularly to alpine ski boot soles.
2. Description of Background and Relevant Information
In a manner which is known in itself, boots comprise a walking sole on which is affixed a vamp, also known as the upper of a boot. For certain purposes, in the field of sports, the walking sole can have different types of structure which are more or less sophisticated, having properties of rigidity, flexibility, shock-absorption, etc. One can cite, by way of example, the walking shoes described in French Patent No. 1,461,743 or German Patent No. 33 21 847, which shoes comprise shock absorbing soles. French Patent No. 1,461,743 teaches in particular a boot whose sole has an insulating hollow structure, which is elastically deformable over only a portion of the walking surface. This structure guarantees a support which is uniformly distributed over the foot in the boot whatever the unevenness of the ground. By way of comparison, German Patent No. 33 21 847 describes one type of shoe in which the shock absorbing sole, extending over the entire walking surface has a deformable structure which substantially modifies the foot retention conditions of the boot.
U.S. Pat. No. 4,619,059, relates to a walking shoe adaptable to ski boots and adapted to be deformed on the side of the walking surface as a function of the unevenness of the ground and of the relative support position on the ground.
The different types of soles described above are not adapted to be utilized on shoes adapted for alpine skiing by virtue both of their lack of rigidity and their excessive coefficient of friction, which renders them incompatible with the retention means of the boot on the ski, commonly referred to as ski bindings, which must themselves satisfy release conditions dictated by safety standards. Thus, these alpine ski boots generally comprise an upper constituted by a shell base whose sole satisfies safety standards and is obtained by molding of a relatively rigid plastic material. Each of the ends of the sole of these boots is thus adapted to come into contact with the bindings of the ski along cooperation zones having dimensional characteristics and a coefficient of friction prescribed by the normalized standards of this type of sport shoe or boot.
Thus, while most of the sport boots must be flexible and offer good shock absorption for the foot with respect to the ground, alpine ski boots must be provided with rigid soles, making it possible to obtain a firm support for the foot which is adapted to guarantee the optimum steering precision of the skis by means of the instantaneous relay of impulses cf the foot of the skier. Furthermore, for the safety reasons explained above, the soles of alpine ski boots must be adapted, at least for the cooperation zones with the bindings, from rigid materials, which resist abrasion and, according to dimensional characteristics, are adapted to satisfy all safety release conditions defined by international standards. However, by virtue of their rigidity and established dimensional constraints, soles of alpine ski boots have a notorious absence of shock absorption. During skiing, the nature of the terrain and the speed of the skier cause a variety of shocks, which are brutally and totally relayed from the ski to the foot of the skier by means of the sole. The forces caused by these shocks, being for the most part directed toward the plane of the sliding surface of the ski, thus create the same number of impact points on the ski, and thus on the sole of the boot, modifying the control conditions and consequent balancing by the skier. Thus, the steering of the skis is itself subjected to forces which are all the more increased and numerous as the skier reaches substantial speeds.